Neural control of smart electromagnetic structures [patch antennas]

Smart electromagnetic structures (SEMS) are capable of interacting with the surrounding electromagnetic field and responding to it. A system is “smart” when it integrates sensing, processing, and control elements (e.g. antennas, neural networks, diodes) in an autonomous manner. A SEMS capable of tuning frequency autonomously is described. Data are presented showing that the system can extend the useable bandwidth of a microstrip patch antenna in a frequency hop environment to more than twice the static value     

History of automotive anticollision radars and final experimentalresults of a MM-Wave car radar developed by the Technical University ofMunich

The history of development of automotive radars in different countries since 1972 is described using a short comparison of radar types. The authors indicate the planning of introduction of car radars in the near future according to information supplied by car companies. The purpose of the development of an automotive radar was to test different signal processing procedures both for distance and Doppler evaluation and also for a digital wavefront reconstruction to find out the angle position of a target. The block diagram, the main properties, the technical data of the radar system, the used antennas and the multiplexing of transmitting antennas is described. Finally some experimental results have been obtained under real traffic conditions     

Optimized RF test range for educational purposes

Both the design and construction of a composite scale airframe and the equipment for an anechoic test range plus the in-house production of absorptive wall covering-all for engineering education-are briefly described. It is shown, that low cost home-made absorbing material with an attenuation of 30 dB or more can be designed. Waveguide and ground plane antennas for test purposes can be constructed from surplus materials. In this case the design and measurements of a 3 GHz antenna pair are shown. Finally, as a test object, a cheap yet effective scale model of a modern fighter aircraft is used for measurements of radar cross section and antenna installations. As a demonstration of the total system capabilities, the measurement of installed F-18 antennas is shown     

应答机对称天线干涉对雷达信号影响分析

针对测速雷达在目标旋转时,由对称天线导致的下行信号干涉问题,通过理论分析远场条件下信号干涉合成方向图变化情况和双基微多普勒计算方法,提出了一种分析干涉区前后多普勒阶跃的方法。通过分析测速雷达记录数据中AGC(Automatic Gain Control,自动增益控制)电平、多普勒和综合误差电压,再利用小波变换和自相关方法,可以提取微多普勒信息和微多普勒周期。理论分析和数据验证可知,信号干涉区出现在对称天线中间±20°左右,雷达接收AGC电平在干涉区下降10~20dB,多普勒差分出现峰值,微多普勒在干涉区前后出现正负峰值,综合误差电压会显著增大。这些结论有利于认识干涉现象对测速设备接收信号的影响。     

Active transmitting phased antenna arrays

The benefits of using transmitting phased array antennas for radar systems are examined. Accurate performance prediction for the transmitting phased array antennas requires theories describing both the antenna system and the power generation devices. These theories were created and applied to the design and performance evaluation of the Russian 3-D mobile solid-state surveillance radar 67N6E (GAMMA-DE), a PAA designed for long-range air defense.     

一种基于角度-多普勒补偿的均匀圆形天线机载雷达杂波抑制方法

采用均匀圆形相控阵天线的机载雷达杂波分布随距离变化而变化,各距离单元的杂波不再满足独立同分布的条件,造成统计型空时自适应处理(STAP)器性能下降。基于此,本文建立了均匀圆形天线机载雷达模型,对其杂波分布进行了分析,得出了空间角随阵元数非线性变化的特性造成其杂波距离维分布非均匀的结论。研究了一种均匀圆形天线机载雷达杂波抑制方法,该方法先通过修正的角度 多普勒补偿(MADC)预处理消除在杂波谱中心处的非均匀,再利用基于导数更新(DBU)技术进一步减小在其他方位杂波的非均匀程度。仿真结果表明了该方法的有效性。     

A low-cost space-based radar system concept

A space-based radar system concept is described that can provide continuous world-wide, all-weather, day-night observation and tracking of ships, aircraft, vehicles and ground facilities of interest. The system employs a constellation of radar satellites in low-earth orbit to provide continuous world-wide target access. The radars employ reflector antennas, TWT transmitters and high frequency (e.g., X band) to achieve long range with relatively low weight, complexity and cost. The radars operate in moving-target-detection (MTD) and synthetic-aperture-radar (SAR) spotlight imaging modes to observe moving and fixed targets, respectively. The system could support a wide range of military, intelligence, law-enforcement and civilian missions     

The ELDORA/ASTRAIA airborne Doppler weather radar: results fromrecent field tests

The ELDORA/ASTRAIA airborne Doppler weather radar was recently placed in service by US and French atmospheric sciences research laboratories. The ELDORA/ASTRAIA radar is designed to provide high resolution measurements of the air motion and rainfall characteristics of atmospheric storms which are too large, remote or fast-moving to be adequately observed by ground-based radars. This paper discusses the measurement requirements and the design goals of the radar and presents sample measurements from a recent weather research field program     

一种基于角度-多普勒补偿的均匀圆形

采用均匀圆形相控阵天线的机载雷达杂波分布随距离变化而变化,各距离单元的杂波不再满足独立同分布的条件,造成统计型空时自适应处理(STAP)器性能下降。基于此,本文建立了均匀圆形天线机载雷达模型,对其杂波分布进行了分析,得出了空间角随阵元数非线性变化的特性造成其杂波距离维分布非均匀的结论。研究了一种均匀圆形天线机载雷达杂波抑制方法,该方法先通过修正的角度-多普勒补偿(MADC)预处理消除在杂波谱中心处的非均匀,再利用基于导数更新(DBU)技术进一步减小在其他方位杂波的非均匀程度。仿真结果表明了该方法的有效性。     

Design of a space-based radar signal processor

Space-based radar (SBR) is capable of providing flexible wide-area coverage of air, land, and sea targets. Numerous studies have been carried out in the United States and Canada in recent years to investigate different concepts for SBR. The design of a suitable radar signal processor (RSP) is challenging due to the effects caused by the moving platform on target integration and clutter spectral spread. A candidate RSP is described that uses a corporate fed array (CFA) antenna as its primary radar sensor. The algorithmic definitions of the signal processing functions are provided; the relationships between these functions and the reasons for their location in the signal processing chain are also discussed. In addition, techniques for reducing the computational requirements are also presented     

基于高度分集的两波束米波雷达测高方法及其应用

米波雷达的波束较宽、由于地面反射引起波瓣分裂,通常只能估高而不能用来测高.针对这一难题本文提出一种基于高度分集的两波束米波雷达测高方法.该方法采用高度不同的两个天线,利用波瓣分裂情况及相互相位关系来测量目标高度.文章分析了此方法测高的精度及影响精度的一些因素.本测高方法已应用于某型雷达信号处理机中,并取得良好效果.     

一种雷达模拟器天线系统设计

该系统采用角锥喇叭天线组成比幅测角系统,介绍了一种用于雷达模拟器的天线系统设计,解决了方位波束宽度大和天线增益高之间的矛盾,具有结构简单、易于实现、天线增益和测角精度高等特点。经测角误差分析和电磁仿真,证明天线系统的增益系数、测角范围和测角精度等主要技术指标满足雷达模拟器设计要求,具有推广应用价值。     

Performance analysis of radar antenna systems

If modern airborne radar systems are to function properly, the radar antenna radiation patterns must meet certain specifications. Until recently, most radar antennas were designed and tested in a clean antenna environment, i.e., there is no near field scattering from host structures or radome effects. However, these higher order effects are the matter of increasing concern with added performance demands in the ever-increasing jammer and clutter interference environments. We investigated the capabilities and limitations of currently available analysis techniques and computer codes for installed performance of airborne radar antenna systems. Then we developed an extended ray-optical technique that could predict total installed performance of airborne radar antenna systems, i.e., the near field scattering from aircraft structures and radome effects. The new analysis technique utilized a ray-tracing method in both airframe and radome simulation. Thus, it can efficiently predict the total installed performance of large radar antenna systems on an aircraft structure     

On a Specific Performance Limitation of Partially Adaptive Antennas

An analysis shows the performance degradation of a sidelobe cancellation system as the consequence of a basic property of partially adaptive antennas when neighboring interference directions are weighted differently in sign by the radar antenna sidelobes.     

Phase Compensation for Widely-Spaced Antenna Systems Employing Coherent Signal Combinations

This paper describes a technique for providing phase compensation to signals received at widely-spaced antennas and processed at a central location. Self-compensation is provided for pathlength variations in reference-signal distribution systems. The technique may be adapted to include the measurement and compensation of signal-channel phase variations. Practical systems which require this type of compensation include interferometric systems used for position and position-rate measurements of missiles and spacecraft, interferometers and arrays of antennas used for radio and radar astronomy, and arrays of large-aperture antennas used for deep-space communications.     

Artificial Beam Sharpening Technique for Radar Beacon Systems

A method of improving angular discrimination artificially in radar beacon systems, without going to extremely high frequencies of operation or using unreasonably large interrogator antennas, involves the use of a null-type antenna pattern superposed on a normal directional beam. The effective are over which replies are obtained is determined by an amplitude discriminator circuit within the beacon which compares the amplitude of the pulse signals received on the null pattern with those received via the directional beam. Only if the latter exceed the former by a predetermined amount does the beacon produce a reply. The method, which has been tried experimentally and its theory verified, produces an increase in traffic handling capacity, as well as improved angular resolution, by reducing unwanted triggering and, hence, clutter on the display and the over-interrogation of transponder beacons. An antenna is described which eliminates triggering on sidelobes by providing the proper current distribution to the radiating elements to cause the null pattern to cover the sidelobes of the normal beam. Triple-pulse amplitude discriminators have been built and tested in a double-pulse interrogation system. Some theoretical considerations and design curves and equations for use in designing nulltype antennas are given in the Appendix.     

CCRS C/X-airborne synthetic aperture radar: An Rand D tool for the ERS-1 time frame

The airborne synthetic-aperture radar (SAR) system developed for the Canada Centre for Remote Sensing (CCRS) is described. It consists of two radars, at C-band and X-band. Each radar incorporates the following features: dual-channel receivers and dual-polarized antennas; a high quality, 7-look, real-time processor; a sensitivity time control for range-dependent gain control; a motion-compensation system for antenna steering in azimuth and elevation; and baseband I and Q signal phase rotation. The system also uses a high-power transmitter with a low-power back-up. The SAR maps to either side of the aircraft, at high or low resolution, at incidence angles which in high resolution span 0° to 80°. Radar operating parameters, data products, key specifications and the motion compensation scheme used are presented. Properties of the real-time imagery are discussed and examples of C-band SAR data in the three operating modes are given     

Doppler Radar Error Equations for Damped Inertial Navigation System Analysis

The use of Doppler radar measurements to provide velocity damping for an aircraft inertial navigation system is considered. Three different Doppler antenna configurations are examined: two-axis stabilized, azimuth stabilized, and data stabilized antennas. A general reference velocity error equation is presented and appropriately evaluated for each of the Doppler configurations. Specific elements of the error equations are examined and physically interpreted for both local-level and space-stable inertial systems. Detailed examination of the interaction of Doppler radar and inertial navigation velocity error mechanisms is provided.     

Netted radar sensing

Future radar applications are beginning to stretch monostatic radar systems beyond their fundamental sensitivity and information limits. Networks of smaller radar systems can offer a route to overcome these limitations; for example, networks of radar sensors can counter stealth technology whilst simultaneously providing additional information for improved target classification. More generally, multiple independent sensors can provide an energetically more efficient collector of radar scatter. The relative merits of non-coherent and coherent networks are introduced and the balance between increased performance, complexity, and cost is discussed.     

GRS 2002: German Radar Symposium in Bonn, Germany

The German Radar Symposium (GRS 2002), organized jointly by the German Institute of Navigation (DGON) and by the Information Technology Society (VDE-ITG), attracted wide interest in the international radar community. It was held from September 3-5, 2002, in Bonn, the former capital city of Germany. The GRS 2002 programme covered a large scale of important radar topics. All classical topics like air traffic control, CFAR, antenna technology, signal processing and simulation papers have been presented and new results were demonstrated. These topics were combined with new applications like meteorology, subsurface, and automotive to underline the increase of interest in radar technology. Phased array antennas are the key elements of high performance multi-function radar systems which are studied all over the world. SAR and ISAR are, nowadays, essential radar techniques for civil and military observation and monitoring.